Distributed storage achieves mass storage and rapid deployment of data by saving data in a plurality of disks of a plurality of servers in a distributed manner. With the update of types of storage devices, new storage devices will continuously join the disk cluster; as a result, distributed storage must support plug-and-play for these storage devices.
Different storage devices have different capacities and performances from each other. How to utilize the space and performance of these storage devices to a maximum degree is a problem needing emphasized concern. Original disk reading and writing strategies mainly concern the space balancing between a disk and a file access server, or use a random polling and selection strategy. Other load balancing technologies in the relevant art mainly concern the selection of a file access server when writing a file according to load information about file access servers at the time when writing the file.
However, the load balancing strategies in the relevant art do not solve the problem of the load brought to the disk by high-frequency access to a hot file when reading out a file, and the system has the following defect: input/output operation per second (IOPS for short) which can be supported by different storage devices are different. At first, fragments for storing a file are selected according to a disk space balancing strategy or random strategy. Under a same load, a high performance storage device can operate stably, but a reading delay phenomenon may occur on a low performance storage device.
In the condition where high and low performance storage devices coexist, the low performance storage device will become a short slab of the performance of all distributed storage devices, and this will be presented more apparently when performing a file reading operation. Just because of the short slab effect of the low performance storage device, the performance difference between different storage devices will lower the overall performance of a disk cluster, resulting in that the performance of the high performance storage device cannot be used maximally.